Apple have retained the ability to merge two PDF files with the built in ‘preview’ app in OSX El Capitan. As with previous versions of OS X, there are 3 different ways that you can do this. 1. You can merge them into 1 document in Preview as you are opening them. 2. You can open them as seperate documents in Preview then merge them by printing them to one pdf file. 3. You can open them as seperate documents in Preview and drag pages from one to the other.

When you open 2 or more PDF documents in preview, depending on how you open them, preview will merge them together into one document OR it can open them as two separate documents. If they are merged then all you need to do is save, but if they have not merged then you need to print them to a new PDF file. Here’s how to tell if they have merged or not.

If you open two documents in preview then have a look at the top of your preview window there is a title with the name of the document. After this title there is a short description in brackets. In this description it will tell you whether there are one or two documents open. See these two examples below.

The title says ‘page 2 of 2’ so the pdf files have merged into one document.

If it says ‘(page 2 of 2)’ like in this top image then the two pdf files have already merged. All you need to do is go to the file menu and click ‘Save’ and the merged files will be saved over the top of the first pdf.

The pdf files have not merged because the title says ‘2 documents’

Here it says ‘2 documents’ meaning that the two files have not yet merged. If you save them they will still save as 2 seperate files. To merge them you will need to select ‘Print’ and then select ‘Save to PDF’ to save the documents to a new pdf file.

If the files have not merged in preview, you can merge them by printing them to PDF.

How to force 2 documents to merge when you open them in Preview

You may be wondering how to force the documents to merge when you open them in Preview. If you just use the ‘Open’ menu from within preview it will open them as two separate documents. If you click on both documents together in the finder it will open them as two separate documents. To force them to merge, you need to open the thumbnail window of the first PDF document (‘View’ then ‘Thumbnails’ from the menubar), and then drag the icon of the second document onto the thumbnail of the first document.

If you drag the second document onto the thumbnail of the first document then this will cause the two documents to merge. If you drag the second document above or below the thumbnail of the first document then the two documents will not merge. So whether they merge or not depends on the location of the second file icon when you let go of your mouse or trackpad button.

Dragging the second file onto the thumbnail of the first file like this will force the two files to merge.

If you drag the second file underneath the thumbnail like this the files will not be merged.

A reminder that if they have not merged you can still merge them by printing them to a new PDF file in the ‘Print’ menu. But if they have merged all you need to do is save them!

Also, if you open two documents in seperate Preview windows, then view the thumbnails, you can selectively drag individual pages across to import single pages into the pdf documents. This will create a partial merge with only the pages that you want.

Thanks for this article, it’s very helpful. I am still struggling to find a way to make Preview preserve the names of the original PDFs as a Table of Contents. Using either the Drag and Drop thumbnail approach or the Print -> Save as PDF will destroy the ToC, which is effectively a marker for each original PDF. Do you know of a way to preserve this information?

-Once the pages are combined in an open PDF file, press Print. -On the Print window, click the “PDF” drop-down in the lower left corner. Select “Save as PDF…” and choose a name and location for your new file. -The file should save as a new, multi-page document.

I’ve been using this method successfully for some time but today when I merged two pdf files and tried to print/pdf/ save as pdf, only the save as postscript is available. The other options are greyed out. any suggestions would be appreciated.

My guess is that one of the files is password protected, and the author of the file has allowed ‘printing’ but not ‘saving’. That would allow you to print (to postscript) but not save (to pdf) the file.